Abstract

BACKGROUND:

The growing burden and morbidity of chronic kidney disease (CKD) warrant effective strategies for identifying those at increased risk. We examined the association of cystatin C level and albuminuria with the development of CKD stage 3.

STUDY DESIGN:

Prospective observational study.

SETTING & PARTICIPANTS:

PREDICTOR:

Participants were categorized into 4 mutually exclusive groups: the presence or absence of microalbuminuria (albumin-creatinine ratio >17 and >25 μg/mg in men and women, respectively) in those with or without cystatin C level ≥1.0 mg/L.

OUTCOMES & MEASUREMENTS:

Incident CKD stage 3 was defined as eGFR <60 mL/min/1.73 m(2) at the third or fourth visit and an annual decrease >1 mL/min/1.73 m(2). Poisson regression was used to evaluate incident rate ratios in unadjusted and adjusted analyses that include baseline eGFR.

RESULTS:

Mean age was 61 years, 49% were men, 38% were white, 11% had diabetes, 13.7% had cystatin C level ≥1 mg/L, 8.4% had microalbuminuria, and 2.7% had cystatin C level ≥1 mg/L with microalbuminuria. 554 (10%) participants developed CKD stage 3 during a median follow-up of 4.7 years, and adjusted incidence rate ratios were 1.57 (95% CI, 1.19-2.07), 1.37 (95% CI, 1.13-1.66), and 2.12 (95% CI, 1.61-2.80) in those with microalbuminuria, cystatin C level ≥1 mg/L, and both, respectively, compared with those with neither.

LIMITATIONS:

Relatively short follow-up and absence of measured GFR.

CONCLUSIONS:

Cystatin C level and microalbuminuria are independent risk factors for incident CKD stage 3 and could be useful as screening tools to identify those at increased risk.

Cystatin C spline evaluating the shape of the relationship with incident rate ratios of chronic kidney disease stage 3 after adjusting for age, gender, and race and excluding the top and bottom 2.5%. Conversion factor for units: Cystatin C in mg/L to nmol/L, ×74.9